Transglutaminases are enzymes that catalyze an acyl transfer reaction of γ-carboxyl amide group of a glutamine residue in a peptide chain. The reaction leads to the formation of ε-(γ-Gln)-Lys cross linking in the intramolecular or intermolecular portion of protein molecules when an ε-amino group of a lysine residue in protein acts as an acyl receptor. Therefore, since the use of the action of a transglutaminase enables protein or peptide to be improved, a transglutaminase of a microbial enzyme derived from the genus Streptomyces is used in binding meat and in manufacturing sausage, bean curd, bread, and noodles (see Patent Document 1).
Transglutaminase is a thiol enzyme having cysteine as an active center residue, and is converted into a mature-form via a pro-form in a fermentation process. Therefore, a transglutaminase has poor stability and requires addition of a stabilizer in order to suppress inactivation during manufacture or storage of products.
As a method for improving stability of a transglutaminase during storage, addition of organic acid, inorganic acid, polyphenol, thiol, and sugar alcohol has been proposed (see Patent Document 1). Furthermore, a method for improving stability by adding protein (wheat protein, soybean protein, and the like), or a partial hydrolysate of protein has been developed (see Patent Document 2). Furthermore, a stabilization technique using trehalose has been developed (Patent Document 3).
[Patent Document 1] Japanese Patent Unexamined Publication No. H4-207194
[Patent Document 2] U.S. Pat. No. 3,651,003
[Patent Document 3] Japanese Patent Unexamined Publication No 2004-305010